U.S. Pat. No. 3,255,793 discloses a Vacuum Comminutor which includes a suction device or blower having a rotor with essentially tangential vanes of special configuration and a central inlet connected to a cylindrical, tubular segment at the larger end of a cone, whose smaller end is connected to a cylindrical tube into which the material to be comminuted is fed. Each rotor vane has a trough like cross section, while a cutting device having a cutting edge facing the blower inlet extends radially into the inlet. The suction produced by the suction blower is stated to induce a flow through the cylindrical tube in the form of an elongated spiral, through the cone in an axially condensed, conical spiral corresponding to the cone and between adjacent blower vanes in a conical spiral. A region of reduced air pressure is stated to be produced within the cone and that as the material passes into the blower casing, explosions of the various particles of the materials occur which reduces or comminutes the particles to smaller size. It is also stated that the theory is that the explosions or comminution of the materials occurs because of the fact that the internal pressures of the particles of the material are greater than the external or air pressure on the particles to a degree that the internal pressures cause a rupturing and a fracturing of the particles into a number of different parts.
The comminutor thus constructed has operated successfully in comminuting material, but has not been successful commerically. It is understood that the vanes of the blower rotor, being subject to comminuted material, have worn so rapidly, particularly at the tips and leading edges, that the expense of replacement has been unduly high. Also, that the wear tends to be uneven, so that undue vibration often requires the rotor to be replaced before any vanes are worn out. It is understood that a very considerable amount of money has been spent in attempting to find a material for the blower rotor vanes which will withstand the wear, as well as redesigning the rotor vanes and/or blower to reduce the wear, but without success.
In the case of a comminutor having a fan with inclined blades rather than the trough-like section of U.S. Pat. No. 3,255,793, but otherwise corresponding thereto, and having a frusto-conical section whose inlet was 6 inches in diameter and outlet was 15 inches in diameter, with the fan driven by a 30 hp motor, the maximum feed which could be achieved was one ton of gold ore per hour. The fan required replacement at the end of 100 hours of operation. The tips of the fan blades were worn razor thin by the passage of particles, although not as small in size as the particles produced by the present invention. Also, the wear was uneven so that the fan became unbalanced, while the ore was damp and tended to build up a crust on the fan blades which was not uniform, accentuating the balance problem. Since the fan shaft was overhanging, the bearings for the shaft also became unduly worn.
Among the objects of this invention are to provide an apparatus for comminuting material in which the material does not engage any rotating or moving parts; to provide a method of comminuting material which is particularly adapted to be carried out by the apparatus of this invention; to provide such a method and apparatus in which a flow of air is produced or induced in a connected series comprising an elongated passage, an expanding frusto-conical chamber, a cylindrical chamber and a larger annular chamber containing a central restrictor, a portion of which extends into the cylindrical chamber; to provide such a method and apparatus in which such flow of air is produced by injection of air generally longitudinally of said passage and tangentially into said cylindrical or annular chamber; to provide such a method and apparatus in which a flow of air is produced in a discharge duct extending tangentially from said annular chamber, as by injecting air generally longitudinally of said duct; to provide such apparatus in which all flow of air may be produced by a source of air, such as a blower, located exteriorly of the passage or chamber; to provide such a method and apparatus which may be varied to accomodate different sizes of material and material having different characteristics; to provide such method and apparatus in which the restrictor may be provided in more than one form and also may be adjustable; to provide such apparatus which is economical to build and operate; and to provide such method and apparatus which is effective and efficient in use.